1. Field of the Invention
The present invention relates to an encrypted stream processing circuit and a method of processing an encrypted stream. More particularly, the present invention relates to an encrypted stream processing circuit and a method of processing an encrypted stream, which are capable of processing an encrypted stream at a high speed.
2. Description of the Related Art
To date, when a stream of a content protected by copyright is transmitted through a bus connected to a CPU (Central Processing Unit), there has been a constraint that it is necessary to encrypt the stream.
Accordingly, when the CPU receives an encrypted stream, it is necessary for the CPU to internally decrypt the stream, to perform predetermined necessary processing on the stream, then to encrypt the stream having subjected to the processing, and to output the stream. That is to say, the CPU performs decryption processing on the stream, predetermined processing on the stream, and encryption processing on the stream by software.
However, execution of such processing by software gives heavy load on the CPU, and thus it is difficult for a CPU having a low processing power to perform processing at a high speed. Also, in order to perform processing at a high speed, a relatively high-speed and expensive CPU becomes necessary.
For example, Japanese Unexamined Patent Application Publication No. 2004-362704 has disclosed a data recording and playback apparatus which protects target copyright without changing copyright protection information described in a stream, and a description has been given that it is not easy to perform processing for rewriting copyright protection information.